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A nucleotide is the basic unit that makes up DNA.
A singular nucleotide is made up of x3 components:
1. A base (1 of 4 molecules = A, T, C or G)
2. 5 Carbon sugar (deoxyribose = DNA or ribose = RNA)
3. Phosphate group (forms a bond between the sugar molecules in a DNA chain = phosphodiester bond)
There are x4 different nitrogenous bases that comprise DNA.
They come under x2 groups depending on their shape and chemical structure.
1. x1 rings = Pyrimidines
2. x2 rings = Purines
Thymine and Cytosine are the smallest of the 4 bases. With only 1 ring in their structure.
Point to Remember!
*** In RNA, Thymine is replaced by Uracil ***
Adenosine and Guanine are the biggest of the 4 bases. Their structure contains a pyrimidine ring + a smaller 5 sided ring. Therefore making a 2 ringed structure.
A nucleotide (base + sugar + phosphate) is the building blocks for nucleic acid (DNA & RNA)
A nucleoside (base + sugar)
Nucleotides can serve as energy carriers in the form of ATP (Adenosine TriPhosphate)
Nucleotides can aid in cell signalling e.g. cyclicAMP (cAMP)
The liver is the largest solid organ in the body as well as the largest gland.
It is made up of 2 large lobes (right lobe bigger than the left lobe). Each lobe is then comprised of much smaller lobules.
Within these lobules lies the cells of the liver, called hepatocytes. It is here that molecules are metabolised.
Absorption of molecules of digestion
In the gut, protein, fats and carbohydrate are broken down into amino acids, lipids and glucose respectively. These are taken from the gut to the liver via the Portal Vein.
The liver is responsible for monitoring the levels of these molecules in the body.
E.g. Straight after a meal:
1. Storage of glucose as glycogen in the hepatocytes "glycogenesis"
2. Storage of lipids in the form of tricglycerides in the adipocytes
3. Formation of proteins to be utlised by the skeletal muscle
In a state of hunger
1. Glygen is broken down into glucose to be used for energy "Glycogenolysis"
2. Amino acids are converted to glucose for energy during starvation "Gluconeogenesis"
3. Once all the glucose has been used up, lipids can be converted to Ketones "ketogenesis" to be utilised by the brain.
*** Glucose is the main source of energy for the brain, when glucose is depleted ketones are utilised ***